1. Field
An apparatus and method for providing a time delay in injection of pressured fluid into a geologic formation. More specifically, it is a toe valve apparatus activated by fluid pressure that opens ports after a predetermined time interval to allow fluid to pass from a well casing to a formation.
2. Background
It has become a common practice to install a pressure responsive opening device at the bottom or toe of a casing string within horizontal well bores and in some vertical bores. These devices make up and run as an integral part of the casing string. After the casing has been cemented and allowed to solidify, the applied surface pressure is combined with the hydrostatic pressure and a pressure responsive valve is opened. The combination of hydrostatic and applied pressure is customarily used to overcome a number of shear pins or to overcome a precision rupture disc. Once communication with the well bore [i.e., area outside of the casing] is achieved, the well can be hydraulically fractured or the valve can be used as an injection port to pump down additional wire line perforating guns, plugs or other conveyance means such as well tractors. Other known methods of establishing communication with the cemented and cased well include tubing conveyed or coil tubing conveyed perforators. These are all common methods to achieve an injection point but require increased time and money.
The present invention provides an improved m apparatus and method that provides a time delay in fluid injection through the casing.